Although grease is used in prior art for lubrication of a bearing of a main electric motor for vehicle, development and researches of bearing structures of oil lubrication have been advanced for the purpose of saving of maintenance because a cracking period is elongated. For bearing structures of oil lubrication in a main electric motor for vehicle there are known those listed in Japanese Unexamined Patent Application Publications No. 62-75195, No. 2003-23747 for example. In a bearing structure described in the '195 and '747 Applications, lubricating oil stored in an oil supply chamber is taken up by a rotation plate mounted on a rotary shaft and is supplied to a bearing box. In the prior art bearing device, a labyrinth structure seals between the oil supply chamber, the bearing box etc. and the outside of the structure to suppress the leakage of oil in the bearing device to the outside of the device.
However, such a constitution of sealing with the labyrinth structure as described above suffers from the leakage of oil to the outside of the device. More specifically, a pressure difference between the inside and outside of the main electric motor is increased owing to temperature rise in the main electric motor for vehicle upon the use of the same, a pressure change in the main electric motor by the rotation of a rotor, and changes in weather and dates upon the use of the main electric motor For this, oil taken up by the oil take-up disk becomes mist and might leak into or out of the device through clearance of the labyrinth.
Further, although it is necessary to effectively supply oil taken up to upper portion by the oil take-up disk, the device disclosed in the above '195 and '747 includes a passage etc. for supplying the lubricating oil taken up by the oil take-up disk to the bearing box. This complicates the structure and makes it difficult to effectively supply the lubricating oil depending on the shape and disposition of the passage.